Petulant desire to drink like Penny (7)
I believe the answer is:
waspish
'petulant' is the definition.
(thesaurus)
'desire to drink like penny' is the wordplay.
'desire' becomes 'wish' (wishing is a kind of desiring).
'to drink' means one lot of letters goes inside another.
'like' becomes 'as'.
'penny' becomes 'p'.
'as'+'p'='asp'
'wish' placed around 'asp' is 'WASPISH'.
(Other definitions for waspish that I've seen before include "Easily-provoked" , "Petulant" , "Bad-tempered like striped insect" , "Bad-tempered like striped stinger" , "'Very irritable, like a stinger (7)'" .)